Dan Christensen wrote:
Dan Christensen <jdc@xxxxxx> writes:
Dan Christensen wrote:
I'm looking at either the Western Digital 500G RE2 drives or the cheaper
500G SE16 drives. I have read that for use with a hardware raid card,
the RE2 drives are more appropriate, and I'm wondering if the same is
true for software raid.
The difference that is most commonly described, and that I should have
highlighted, is TLER: Time-Limited Error Recovery. Apparently, the SE16
drives can take a long time to recover from an error (up to two minutes,
I believe), and hardware raid controllers can kick the drives out of the
array when it would instead be better for the drive to return a
read/write error and let the raid controller deal with it.
My question is really whether this logic applies to linux software raid.
One more reference:
http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery
It certainly sounds to me like TLER is also appropriate for software
raid, so I'm going to go ahead and get the RE2 drives.
Dan
If you were trying to salvage as much data as possible off of a drive TLER would
also be nice, since it would lower the time to get a bad sector error.
I don't really understand how much use it is to try that many times, the drive
should be able to try 1x per rev, so at 7200, 120 times per second, I would
wonder how many times that they get a good read after having failed the first
120 times, much less after the first 7 seconds (960 failures) of trying, or even
longer periods without TLER.
In fact I would think for a RAID drive one would want even lower than 7 seconds.
Roger
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